Method of bonding porous metal to metal substrates

ABSTRACT

A method for preparing an implant having a porous metal component. A loose powder mixture including a biocompatible metal powder and a spacing agent is prepared and compressed onto a metal base. After being compressed, the spacing agent is removed, thereby forming a compact including a porous metal structure pressed on the metal base. The compact is sintered, forming a subassembly, which is aligned with a metal substrate portion of an implant. A metallurgical bonding process, such as diffusion bonding, is performed at the interface of the subassembly and the metal substrate to form an implant having a porous metal component.

INTRODUCTION

The present technology relates to medical implants containing a porousmetal component and methods of their manufacture. In the growing fieldof medical devices, there is continued need to provide lightweightorthopedic implants having enhanced strength, such as implants withporous metal that can provide a three-dimensional space for bonein-growth.

Joining porous metal to a metal substrate for use with an implant can bechallenging, however, because the contact points available at theinterface of the materials may be limited due to the surface morphologyof the porous metal construct. While various methods are known forjoining powder metal materials to a metal substrate, such as sintering,welding, and brazing, there are many drawbacks. The high temperatures ofsintering may affect substrate properties. Welding and brazing typicallyuse filler materials that can adversely affect biocompatibility of thefinal device for medical applications. Thus, it would be desirable toprovide a method for joining powder metal to an implant that operates ata lower temperature and does not require additional filler materials.Specifically, it is desirable to use diffusion bonding techniques tojoin a porous metal structure to a metal substrate for use in animplant.

SUMMARY

The present technology provides methods for preparing an implant havinga porous metal component. In various embodiments, the method includespreparing a loose powder mixture including a biocompatible metal powderand a spacing agent. The powder mixture is compressed onto a metal base.After being compressed, the spacing agent is removed, thereby forming acompact, which comprises a porous metal structure pressed on the metalbase. The method includes sintering the compact, forming a subassemblyhaving a porous metal component and a metal base, and aligning thesubassembly with a metal substrate component of the desired finalimplant. A metallurgical bond is formed between the subassembly and themetal substrate component. In various embodiments, the metal base of thesubassembly is diffusion bonded to the metal substrate to form animplant having a porous metal component.

In other embodiments, the method for preparing an implant having aporous metal component includes preparing a loose powder mixturecomprising a biocompatible metal powder and a spacing agent, andcompressing the powder mixture onto a metal base defining a metalsurface. The metal base can be from a solid stock of metal material orcan be a layer of powder metal material. The powder mixture is heated toremove the spacing agent and to define a plurality of pores therein,forming a compact. The compact is then sintered, forming a subassemblyincluding a porous metal structure having a metal backing. The metalbacking of the subassembly is then aligned with a metal substratecomponent of the desired final implant. The method includes diffusionbonding the metal backing to the metal substrate to form an implanthaving a porous metal component.

Still in other embodiments, the method for preparing an implant having aporous metal component includes filling or otherwise placing a baselayer comprising a biocompatible metal powder into a mold. A loosepowder mixture of a biocompatible metal powder and a spacing agent isprepared. The method includes spreading the loose powder mixture intothe mold on top of the base layer, forming a secondary layer. Acompressive force is applied to the mold, thereby concurrentlycompressing the loose powder mixture of the secondary layer, compressingmetal of the base layer, and pressing the secondary layer onto the baselayer. The spacing agent is removed, defining a plurality of poreswithin the secondary layer. The method further includes sintering themold contents and forming a subassembly including a porous metalstructure having a powder metal backing. The powder metal backing of thesubassembly is then diffusion bonded to a metal substrate portion of animplant, forming an implant having a porous metal component.

DRAWINGS

FIG. 1 is a flow diagram illustrating a method for preparing a porousmetal implant.

FIGS. 2A-2F illustrate certain embodiments of making a compact andsubassembly of the present technology including a porous metal structureand a metal base.

FIGS. 3A-3D illustrate another embodiment of making a compact andsubassembly including a porous metal structure and a powder metal base.

FIGS. 4A and 4B illustrate diffusion bonding a subassembly to a metalsubstrate.

FIG. 5A is an exemplary acetubular cup shaped medical implant having aporous metal component attached thereto.

FIG. 5B is a cross section of FIG. 5A taken along the line 5B-5B.

In the Figures, certain reference numerals indicate corresponding partsthroughout the several views of the drawings.

It should be noted that the figures set forth herein are intended toexemplify the general characteristics of materials, methods and devicesamong those of the present technology, for the purpose of thedescription of certain embodiments. These figures may not preciselyreflect the characteristics of any given embodiment, and are notnecessarily intended to define or limit specific embodiments within thescope of this technology.

DETAILED DESCRIPTION

The following description of technology is merely exemplary in nature ofthe subject matter, manufacture and use of one or more inventions, andis not intended to limit the scope, application, or uses of any specificinvention claimed in this application or in such other applications asmay be filed claiming priority to this application, or patents issuingtherefrom.

The headings (such as “Introduction” and “Summary”) and sub-headingsused herein are intended only for general organization of topics withinthe present disclosure, and are not intended to limit the disclosure ofthe technology or any aspect thereof. In particular, subject matterdisclosed in the “Introduction” may include novel technology and may notconstitute a recitation of prior art. Subject matter disclosed in the“Summary” is not an exhaustive or complete disclosure of the entirescope of the technology or any embodiments thereof. Classification ordiscussion of a material within a section of this specification ashaving a particular utility is made for convenience, and no inferenceshould be drawn that the material must necessarily or solely function inaccordance with its classification herein when it is used in any givencomposition.

The description and specific examples, while indicating embodiments ofthe technology, are intended for purposes of illustration only and arenot intended to limit the scope of the technology. Moreover, recitationof multiple embodiments having stated features is not intended toexclude other embodiments having additional features, or otherembodiments incorporating different combinations of the stated features.Specific examples are provided for illustrative purposes of how to makeand use the compositions and methods of this technology and, unlessexplicitly stated otherwise, are not intended to be a representationthat given embodiments of this technology have, or have not, been madeor tested.

As used herein, the words “desirable”, “preferred” and “preferably”refer to embodiments of the technology that afford certain benefits,under certain circumstances. However, other embodiments may also bepreferred or desirable, under the same or other circumstances.Furthermore, the recitation of one or more preferred embodiments doesnot imply that other embodiments are not useful, and is not intended toexclude other embodiments from the scope of the technology.

As referred to herein, all compositional percentages are by weight ofthe total composition, unless otherwise specified. As used herein, theword “include,” and its variants, is intended to be non-limiting, suchthat recitation of items in a list is not to the exclusion of other likeitems that may also be useful in the materials, compositions, devices,and methods of this technology. Similarly, the terms “can” and “may” andtheir variants are intended to be non-limiting, such that recitationthat an embodiment can or may comprise certain elements or features doesnot exclude other embodiments of the present technology that do notcontain those elements or features.

Although the open-ended term “comprising,” as a synonym ofnon-restrictive terms such as including, containing, or having, is usedherein to describe and claim embodiments of the present technology,embodiments may alternatively be described using more limiting termssuch as “consisting of” or “consisting essentially of.” Thus, for anygiven embodiment reciting materials, components or process steps,Applicants specifically envision embodiments consisting of, orconsisting essentially of, such materials, components or processesexcluding additional materials, components or processes (for consistingof) and excluding additional materials, components or processesaffecting the significant properties of the embodiment (for consistingessentially of), even though such additional materials, components orprocesses are not explicitly recited in this application. For example,recitation of a composition or process reciting elements A, B and Cspecifically envisions embodiments consisting of, and consistingessentially of, A, B and C, excluding an element D that may be recitedin the art, even though element D is not explicitly described as beingexcluded herein.

As referred to herein, all compositional percentages are by weight ofthe total composition, unless otherwise specified. Disclosures of rangesare, unless specified otherwise, inclusive of endpoints. Thus, forexample, a range of “from A to B” or “from about A to about B” isinclusive of A and of B. Disclosure of values and ranges of values forspecific parameters (such as temperatures, molecular weights, weightpercentages, etc.) are not exclusive of other values and ranges ofvalues useful herein. It is envisioned that two or more specificexemplified values for a given parameter may define endpoints for arange of values that may be claimed for the parameter. For example, ifParameter X is exemplified herein to have value A and also exemplifiedto have value Z, it is envisioned that parameter X may have a range ofvalues from about A to about Z. Similarly, it is envisioned thatdisclosure of two or more ranges of values for a parameter (whether suchranges are nested, overlapping or distinct) subsume all possiblecombination of ranges for the value that might be claimed usingendpoints of the disclosed ranges. For example, if parameter X isexemplified herein to have values in the range of 1-10, or 2-9, or 3-8,it is also envisioned that Parameter X may have other ranges of valuesincluding 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, and 3-9.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on”, “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The present technology provides methods for preparing a medical implant,including joining a porous metal component to a metal substrate of animplant. As used herein, the term “implant” may be used to refer to anentire implant, or a portion thereof. For example, an implant made inaccordance with the present technology, having a porous metal componentjoined thereto, may constitute the entire implant, or it may be usedwith one or more other pieces or components that together form a finalimplant or implant assembly. One or more portions of the implant may beprovided with a metal substrate external surface or the entire implantmay define a continuous surface having a metal substrate. Generally,“joined” and “joining” are comprehensive terms used to describe allprocesses that affix one part to another. Many useful joining/weldingprocesses provide the application of heat with controlled melting ofbase materials and a filler metal. Other useful joining processes relyon surface diffusion or solid state mechanical interlocking. Manyoptions are available for specifically joining powder metal materials toa metal substrate portion of an implant, including sintering, variouswelding techniques, and brazing. However, the high temperatures ofsintering may affect substrate properties, while the filler materialsused in welding and brazing techniques can adversely affectbiocompatibility of the final device for medical applications. Forexample, cobalt may melt at typical sintering temperatures.

With diffusion bonding (sometimes called sinter bonding), no additionalmaterials are required to form a bond because the bonding relies onatomic diffusion between substrates. Accordingly, diffusion bondingtechniques are attractive for biocompatible applications, providing avery clean solid state bond resulting from mechanical interlocking andalloy diffusion occurring at the joining interface of the matingcomponents. Because diffusion bonding is conducted at lowertemperatures, relative to sintering or welding, the formation ofintermetallic eutectics at the joining interface is minimized or avoidedaltogether. In order to maintain strong and uniform bond strength,however, effective diffusion bonding may be limited by geometries. Forexample, the strength of a bond can be related to the number of contactpoints between the two mating components. Accordingly, joining a porousmetal component directly to a metal substrate or a metal component of animplant by diffusion bonding can pose a problem because the number ofcontact points available at the joining interface between the twosubstrates may be limited to the particular surface morphology of theporous metal construct. Having such a limited contact area for bondingmay make it difficult to achieve bonds strengths suitable for orthopedicapplications.

The present technology provides methods for preparing a porous metalconstruct with a thin, integral, solid metal backing or metal base. Asused herein, the terms “solid metal backing,” “solid metal base,” and“metal base” generally refer to a substantially non-porous metalbacking, or base, that may include, as non-limiting examples, a solidmetal or a compressed powder metal. This non-porous backing, or base,assists in creating a smooth surface-joining interface with an increasedsurface/contact area that yields a very strong, mechanically stable bondbetween the porous metal component and metal substrate portion of animplant when using diffusion bonding techniques.

With reference to FIG. 1, which generally depicts steps of variousembodiments of the present technology, a loose powder mixture is in step100. The loose powder mixture can comprise a biocompatible metal powderand a spacing agent, or porogen material. The metal powder can be anymetal or alloy that is suitable for use as an implant and provides thedesired strength and load bearing capabilities. Suitable exemplarymetals include titanium, cobalt, chromium, or tantalum, alloys thereof,stainless steel, iron alloys, and combinations thereof. The metal powderparticles can have a diameter ranging from between about 5 micrometersto about 1500 micrometers. In various embodiments, the metal powderparticles have a diameter from between about 100 micrometers to about500 micrometers, in other embodiments the metal powder particles canhave a diameter from between about 75 micrometers to about 175micrometers. The metal powder can be a mixture of at least two differentparticle sizes. For example, it may contain a first portion from a firstmixture of metal particles having a diameter of between about 150 toabout 250 micrometers and a second portion from a second mixture ofmetal particles having a diameter of between about 250 and about 425micrometers. In certain embodiments, larger metal beads may be used.

In step 102, the loose metal mixture is compressed together and pressedonto a metal base. Such a metal base can be a solid metal, as will bediscussed below. The chemical composition of the metal base can beidentical to that of the metal powder, or the composition of the metalbase can be different from that of the metal powder. In variousembodiments, the compression of the powder mixture includes applying anisostatic pressing technique at ambient temperature, or using coldisostatic pressing (CIP). The CIP can use a water or air mixturepressurized up to the desired pressure range of from about 5,000 toabout 100,000 psi. In various embodiments, the pressure range is fromabout 50,000 to about 75,000 psi, or about 60,000 psi.

The spacing agent, or porogen particles, of the loose powder mixtureprovides the pores of the porous metal implant. The spacing agent can beremovable from the mixture and it may be desirable if the spacing agentdoes not leave residue in the porous metal implant. It may be furtherdesirable that the spacing agent expands or contracts to supplement theformation of pores of a desired size within the porous metal implant.The pores may range in size of from between about 1 to about 1,000micrometers, or as otherwise desired. For example, in certainembodiments, it may be desirable to have a pore size from about 100 toabout 600 micrometers. In other embodiments, it may be desirable to havea pore size from between about 500 to about 700 micrometers. The spacingagent can be selected from the group consisting of hydrogen peroxide,urea, ammonium bicarbonate, ammonium carbonate, ammonium carbamate,calcium hydrogen phosphate, naphthalene, and mixtures thereof, or can beany other suitable subliming and space forming material. Generally, thespacing agent has a melting point, boiling point, sublimationtemperature, etc. of less than about 400° C., or less than about 350°C., depending on the specific materials used.

A non-polar liquid binder can be used to improve the cohesiveness of themixture because the non-polar liquid binder keeps all mixture componentsin close proximity and does not dissolve the spacing agent. Thenon-polar liquid binder can be a volatile compound with a boiling pointsufficiently close to the sublimation or decomposition point of thespacing agent. In various embodiments, that temperature difference isless than about 200° C. In still other embodiments, that difference isless than about 100° C. The close range of the sublimation temperatureof the spacing agent and the boiling point of the non-polar liquidbinder allows for a single step removal of the spacing agent and thenon-polar liquid binder during thermal processing.

The mixture of non-polar liquid binder, spacing agent, and metal powdercan be made homogenous by mixing as is known in the art. In variousembodiments, the ratio of metal powder to spacing agent can be fromabout 1:1 up to about 10:1, or greater. The non-polar liquid binder canbe in a ratio of from about 1 part binder (in milliliters) to about 10parts of solid (spacing agent and biocompatible metal powder, in grams)up to about 1 part binder 16 to about 30 parts of solid. Altering theratios of the mixture components and/or the particle sizes of thecomponents can provide an implant having a higher or lower porosity,enhanced load-bearing abilities, or can help to tailor the porous metalimplant for a particular region of the body. Utilizing a ratio of metalpowder to spacing agent of 8:1 will provide a dense implant having veryfine pores. In another example, in a mixture having a 3:1 metal powderto spacing agent ratio, if the spacing agent has a diameter of at leastabout 25 micrometers and the metal powder has a diameter of about 10micrometers, large pores result. If the metal powder and spacing agentdiameter sizes were reversed, smaller pores would result.

As previously mentioned, the mixture can also include metal powders ofdifferent particulate sizes. By including metal powder particulates ofat least two different sizes, a porosity gradient can be achieved. Theporosity gradient can be such that the porosity of the implant increasesor decreases by up to about 80% across the body of the implant. Theporosity gradient can be continuous and scale up (or down) to a desiredamount, or the porosity gradient can include differing porosity regions(e.g., 80% porosity region transitions to a 40% porosity region whichtransitions to a 75% porosity region). The transitions between theregions can be continuous in the porous metal implant. To provide thedifferent porosities, a mixture corresponding to a particular porosityis stacked on top of or adjacent to a mixture having a differentporosity.

With further reference to FIG. 1, once compressed and pressed onto themetal base, thermal processing is carried out and formation of a compactin step 104. The spacing agent provides the macroporosity andmicroporosity of the biocompatible metal powder before and during theinitial thermal processing because after the spacing agent decomposes,pores or gaps remain between the metal powder particles where thespacing agent was located. The spacing agent particles can have asuitable particle diameter such that the final porosity of the porousmetal portion is between about 65% to about 70%, or other porositysuitable for use with a medical implant.

The thermal processing step 104 includes removing the spacing agent andthe non-polar liquid binder and forming a compact. In an exemplarymethod, the compact can be initially heated at from about 50° C. toabout 350° C. or about 400° C. to remove the non-polar liquid binder andthe spacing agent. The exact temperature can be selected depending onthe combination of the non-polar liquid binder and the spacing agent,vacuum conditions, etc. It is desirable to remove the spacing agent at atemperature at which the metal does not react with the spacing agent. Invarious embodiments, that temperature can range from about 25° C. toabout 500° C. In various other embodiments, that temperature can be atemperature less than the melting point of the metal powder. A suitableinitial temperature can be at about at least 60° C. or higher, butpreferably under the sintering temperature of the selected metal powder.It may be desirable for the initial temperature to be at about or abovethe boiling point or the sublimation point or decomposition of thebinder component having the highest temperature value.

In step 106 the compact is sintered to create a subassembly including aporous metal structure and a metal base. As is known in the art,sintering creates metallic interparticle bonds that provide certainphysical and mechanical properties of the porous metal implant.Sintering conditions (temperature, time, and atmosphere) should be suchthat the metallic interparticle bonds are created while extensivedensification is avoided. The sintering can be performed in a controlledatmosphere, such as a vacuum (for example, at 10⁻⁵ torr) or underreduced pressure. It may be desirable to conduct the sintering in aninert atmosphere, for example, where the atmosphere is flushed withargon or helium gas prior to initiating the vacuum. Such a vacuum and/orthe inert atmosphere will minimize or prevent solid solution hardeningof the surface of the porous implant as a result of inward diffusion ofoxygen and/or nitrogen into the metal and to prevent formation of oxideson the metal surface. The sintering process can occur using asingle-oven or furnace process.

Sintering can be performed at once or in stages. A first sintering ofthe compact can be conducted to transform the compact (substantiallyfree from metallurgical bonds between the metal powder particles) to thesubassembly having metallurgical bonds. The temperature can be increasedin a furnace or chamber (by 2° C., 5° C., 10° C., 20° C., 50° C., forexample) at time intervals (from 5 seconds to 15 minutes). Once thedesired temperature or “hold temperature” is reached, which will varyfor the particular metals, the compact is maintained at the holdtemperature from about 1 hour to about 10 hours or from about 2 hours toabout 6 hours to create the metallurgical bonds between the metal powderparticles. The use of temperature intervals can allow for theelimination of separate steps or separate ovens used to remove thespacing agent and the non-polar liquid binder, if used. In variousaspects, the step of sintering the compact includes sintering adjacentparticles of the porous metal structure to one another and concurrentlysintering the porous metal structure to the metal base, providing anintegral subassembly.

Once sintered, the subassembly is aligned with a metal substrate portionof an implant, in step 108. As discussed above, the metal substrate maybe provided on certain portions of the implant, or in other embodiments,the metal substrate may be on an entirety of the implant. Suitableexemplary metal substrates include Ti6Al4V, CoCrMo alloys (F75 as-cast,F75 HIP-HT, F1537 high C and low C wrought), and commercially puretitanium. In various embodiments, the metal substrate can be speciallyprepared prior to aligning and attaching the porous body. For example,the porous metal structure, the metal substrate portion, or both, can bemachined to a desired shape prior to forming the metallurgical bondbetween the subassembly and the metal substrate. In certain embodiments,the machining may take place after forming the metallurgical bond.Machining may be performed with an accuracy of between about ten andtwenty thousandths of an inch, depending upon the equipment. The metalsubstrate can be acid etched, subjected to an acid bath, grit blasted,or ultrasonically cleaned for example. Other preparations include addingchannels, pits, grooves, indentations, bridges, or holes to the metalsubstrate. Depending on the overall geometry, these additional featuresmay increase the attachment of the porous metal structure to theunderlying metal substrate. Once aligned, a metallurgical bond is formedbetween the subassembly and the metal substrate portion as referenced bymethod box 110. In various embodiments, forming the metallurgical bondincludes diffusion bonding the metal base of the subassembly to themetal substrate portion, creating an implant having a porous metalcomponent.

After diffusion bonding, the porous metal containing implant can bequenched or rapidly cooled. Quenching can be achieved by directquenching, fog quenching, hot quenching, interrupted quenching,selective quenching, slack quenching, spray quenching, and/or timequenching. Quenching can be performed in the diffusion bonding ovenwithout moving the implant. For example, with fog quenching, a fog couldbe distributed through the oven to quench the metal and the fog could besubsequently vacuumed out. In various other embodiments, the cooling canoccur for a time period of between about 3 hours and about 20 hours inan inert atmosphere.

The porous metal containing implant can also be attached as part of anorthopaedic insert, such as those disclosed in U.S. patent applicationSer. No. 12/038,570 filed Feb. 27, 2008 and published as U.S. PatentApplication Publication No. 2008/0147187, Bollinger et al., publishedJun. 19, 2008, which is incorporated by reference herein in itsentirety. The porous metal containing implant can also be used to form ageostructure, which is a three-dimensional geometric porous engineeredstructure that is self supporting and is constructed of rigid filamentsjoined together to form regular or irregular geometric shapes. Thestructure is described in more detail in U.S. Pat. No. 6,206,924, Timm,issued Mar. 27, 2001 which is incorporated by reference.

In various embodiments, optional agents can be coated onto or in asurface of the porous metal component of the implant. Such optionalmaterials include ceramics, polymers, bone materials, blood products,bioactive materials, and combinations thereof. Such ceramics includeresorbable or non-resorbable ceramic materials, such as glasses orceramics comprising mono-, di-, tri-, α-tri-, β-tri-, and tetra-calciumphosphate, hydroxyapatite, calcium sulfates, calcium oxides, calciumcarbonates, magnesium calcium phosphates, phosphate glass, bioglass, andmixtures thereof. Polymers include resorbable or non-resorbablepolymers, such as polyhydroxyalkanoates, polylactones and theircopolymers. Such polymers include poly(L-lactic acid) (PLLA),poly(D,L-lactide), poly(lactic acid-co-glycolic acid), 50/50(DL-lactide-co-glycolide), polydioxanone, polycaprolactone andco-polymers and mixtures thereof such aspoly(D,L-lactide-co-caprolactone). Bone products include bone powder anddemineralized bone. Blood products include blood fractions and otherblood derived materials, such as platelet rich plasma. Bioactive agentsuseful herein include organic molecules, proteins, peptides,peptidomimetics, nucleic acids, nucleoproteins, antisense molecules,polysaccharides, glycoproteins, lipoproteins, carbohydrates andpolysaccharides, botanical extracts, and synthetic and biologicallyengineered analogs thereof, living cells such as stem cells (e.g.,adipose derived stem cells) chondrocytes, bone marrow cells, viruses andvirus particles, natural extracts, and combinations thereof. Specificexamples of bioactive materials include hormones, antibiotics and otherantiinfective agents, hematopoietics, thrombopoietics, agents, antiviralagents, antiinflammatory agents, anticoagulants, therapeutic agents forosteoporosis, enzymes, vaccines, immunological agents and adjuvants,cytokines, growth factors, cellular attractants and attachment agents,gene regulators, vitamins, minerals and other nutritionals,nutraceuticals and combinations thereof. For example, the optionalmaterial may be a resorbable ceramic, resorbable polymer, antimicrobial,demineralized bone, blood product, stem cell, growth factor or mixturethereof. In various embodiments the optional materials facilitateingrowth of new tissue into the porous metal implant.

FIGS. 2A-2F illustrate certain embodiments of making a compact andsubassembly of the present technology including a porous metal structureand a metal base. In various embodiments, the metal base can be providedas a layer of powder metal material. As shown in FIG. 2A, a layer ofbiocompatible metal powder 10 can be added to a suitable mold 12 and iscompressed and/or sintered to form a substantially non-porous metal base14 as shown in FIG. 2C. In another embodiment, as shown in FIG. 2B, themetal base 14 can be provided as a solid layer taken from a solid blockof metal 16. Once the metal base 14 is obtained (from any method), itcan be placed in a suitable mold 12, as shown in FIG. 2D. The loosepowder mixture is then prepared and can be spread in the mold 12 on topof the metal base 14 forming a secondary layer 18 that can include metalpowder 20, spacing agent 22, and an appropriate binder 24 as shown inFIG. 2E. A compressive force can then be applied to the mold contents,thereby compressing the loose powder mixture of the secondary layer 18,and pressing the secondary layer 18 onto the base layer 14. The spacingagent 22 and binder 24 are subsequently removed during thermalprocessing, forming pores 26 in their locations and leaving a compact 28including a porous metal structure having a thin metal backing 30 asshown in FIG. 2F. In various embodiments, the porous metal portion ofthe compact 18 may be provided having a thickness of between about 1 toabout 5 mm (0.04 to about 0.2 inches), or between about 2 to about 4 mm(0.08 to about 0.16 inches), while the metal backing 30 can be providedhaving a thickness of less than about 3 mm (about 0.12 inches), or lessthan about 2 mm (about 0.08 inches). In certain embodiments a thicknessof as little as 0.5 mm (about 0.02 inches) can be used so as to not addadditional weight or take up valuable space. The compact 28 can besubsequently sintered to form a subassembly, which is then diffusionbonded to a metal substrate portion of an implant, incorporating aporous metal component with a medical implant as described above.

FIG. 3A-3D illustrate another embodiment of making a compact andsubassembly including a porous metal structure and a powder metal base.As shown in FIG. 3A, a mold 12 is provided with a layer of biocompatiblemetal powder 10 to form a base layer. Prior to compressing the baselayer, the loose powder mixture is prepared and spread into the mold 12on top of the metal powder 10, forming a secondary layer 18 that caninclude metal powder 20, spacing agent 22, and an appropriate binder 24as shown in FIG. 3B. Thereafter, the compressive force can be applied tothe mold contents, compressing the loose powder mixture of the secondarylayer 18, compressing the loose metal powder 10 of the base layer, andpressing the secondary layer 18 onto the base layer 14. The spacingagent 22 and binder 24 are subsequently removed during thermalprocessing, forming pores 26 in their locations and leaving a compact 28including a porous metal structure having a thin metal backing 30 asshown in FIG. 3D. The compact can be subsequently sintered to form asubassembly, diffusion bonded to a metal substrate, and incorporatedinto a medical implant as described above.

FIGS. 4A and 4B illustrate diffusion bonding a sintered subassembly 32to a metal substrate 34. As shown in FIG. 4A, the metal base 30 caninclude a solid, or substantially non-porous, metal backing surface 36and the metal substrate 34 can include a solid, or substantiallynon-porous, metal face 38. The diffusion bonding occurs at an interfacecreated between the solid metal backing surface 36 and the solid metalface 38 and creates a uniform diffusion bond 40 extending along theentire joining interface as shown in FIG. 4B. Such diffusion bonding canoccur along the entire interface and can be performed with theconcurrent addition of pressure. In certain embodiments it may bedesirable to maintain a compressive force of between about 1 and about200 psi. Because bonding occurs along the entire interface, as opposedto limited contact points, the present technology may only requiremaintaining a compressive for of between about 10 psi and about 30 psiat the interface. For example, the pressure could be maintained at about20 psi at the interface with favorable results.

The present technology may be used with implants having a wide range ofsizes and geometrical configurations. FIG. 5A illustrates an exemplaryacetubular cup medical implant 50 having a porous metal component 52attached thereto. FIG. 5B is a cross sectional view of FIG. 5A, takenalong the line 5B-5B and further illustrates the bond 40 between themetal substrate 34 of the implant 56 and the metal base 30 portion ofthe porous metal component 52. It is envisioned that such a porous metalcomponent can be used with any type of implant that ultimately contactsor is near bone and would be beneficial for bone in-growth. Variousother non-limiting implants include hip stems, knee femorals, primarytibial trays, wrist reconstructive systems, and various claw devices.

The embodiments described herein are exemplary and not intended to belimiting in describing the full scope of compositions and methods of thepresent technology. Equivalent changes, modifications and variations ofembodiments, materials, compositions and methods can be made within thescope of the present technology, with substantially similar results.

1. A method for preparing an implant having a porous metal component,comprising: a. preparing a loose powder mixture comprising abiocompatible metal powder and a spacing agent; b. compressing thepowder mixture onto a metal base; c. removing the spacing agent to forma compact having a porous metal structure pressed on the metal base; e.sintering the compact to form a subassembly; f. aligning the subassemblywith a metal substrate component; and g. forming a metallurgical bondbetween the subassembly and the metal substrate component to form animplant.
 2. The method of claim 1, wherein forming a metallurgical bondbetween the subassembly and the metal substrate component comprisesdiffusion bonding the metal base of the subassembly to the metalsubstrate component.
 3. The method of claim 2, wherein the metal basecomprises a metal backing surface, the metal substrate componentcomprises a metal face, and the diffusion bonding occurs at an interfacebetween the metal backing surface and the metal face.
 4. The method ofclaim 1, wherein the biocompatible metal powder is selected from thegroup consisting of titanium, titanium alloys, cobalt, cobalt alloys,chromium, chromium alloys, tantalum, tantalum alloys, iron alloys,stainless steel, and mixtures thereof.
 5. The method of claim 1, whereinthe step of sintering the compact comprises concurrently sinteringadjacent particles of the porous metal structure to one another andsintering the porous metal structure to the metal base.
 6. The method ofclaim 1, wherein the spacing agent comprises ammonium bicarbonate andremoving the spacing agent comprises heating the powder mixture.
 7. Themethod of claim 1, wherein compressing the powder mixture onto the metalbase comprises applying an isostatic pressing technique at ambienttemperature.
 8. The method of claim 1, wherein the porous metalstructure and the metal base have the same chemical composition.
 9. Themethod of claim 1, wherein the metal base is a solid metal layer ofmaterial taken from a solid metal block.
 10. The method of claim 1,wherein the metal base is a non-porous layer of powder metal material.11. The method of claim 1, further comprising machining one or both ofthe porous metal structure and the metal substrate, prior to forming themetallurgical bond between the subassembly and the metal substrate. 12.The method of claim 1, further comprising machining one or both of theporous metal structure and the metal substrate, after forming themetallurgical bond between the subassembly and the metal substrate. 13.The method of claim 1, further comprising coating at least a surface ofthe porous metal implant with material selected from the groupconsisting of resorbable ceramics, resorbable polymers, antimicrobials,demineralized bone, blood products, stem cells, growth factors, andmixtures thereof.
 14. A method for preparing an implant having a porousmetal component, comprising: a. preparing a loose powder mixturecomprising a biocompatible metal powder and a spacing agent; b.compressing the powder mixture onto a metal base defining a metalsurface; c. heating the compressed powder mixture and defining aplurality of pores therein to form a compact; e. sintering the compactto form a subassembly comprising a porous metal structure having anon-porous metal backing; f. aligning the metal backing of thesubassembly with a metal substrate component; and g. diffusion bondingthe metal backing to the metal substrate component to form an implant.15. The method of claim 14, further comprising cooling the implant for atime period of from about 3 hours to about 20 hours in an inertatmosphere after the diffusion bonding.
 16. The method of claim 14,wherein the diffusion bonding occurs along an interface between thenon-porous metal backing and the metal substrate and comprisesmaintaining a compressive force of about 20 psi at the interface. 17.The method of claim 14, comprising providing the metal backing with afinal thickness of about 0.5 mm.
 18. A method for preparing an implanthaving a porous metal component, comprising: a. placing a base layercomprising a biocompatible metal powder into a mold; b. preparing aloose powder mixture of a biocompatible metal powder and a spacingagent; c. forming a secondary layer by spreading the loose powdermixture in the mold on top of the base layer; d. applying a compressiveforce to the mold thereby compressing the loose powder mixture of thesecondary layer, compressing the base layer, and pressing the secondarylayer onto the base layer; e. removing the spacing agent, defining aplurality of pores within the secondary layer; f. sintering the moldcontents, forming a subassembly including a porous metal structurehaving a powder metal backing; and g. diffusion bonding the powder metalbacking of the subassembly to a metal substrate component of an implant,forming an implant.
 19. The method of claim 18, wherein the steps ofremoving the spacing agent and sintering the mold contents are carriedout in a vacuum environment.
 20. The method of claim 18, whereinsintering the mold contents comprises placing the mold in a furnaceenvironment having a temperature and pressure sufficient to obtain aporous metal structure with a non-porous metal backing.